Lee Garth twisted in his chair. Wearily he laid the pencil down. The equations wouldn't work right. They kept trying to run off into impossible combinations. There was an erratic but persistent gadfly of thought buzzing in his mind, a vague shadowy movement in his brain. Like a ghost from shadow-land it twisted through his brain, twisting through the dark convolutions where his memory lay testing the open synapses, seeking a place where a short circuit would result in action.
Fretfully, Lee Garth picked up the pencil. But there was a thinking in his mind, a formless thinking that was somehow purposeful. He sensed the import of that purpose. Tiny chills ran over his body, tiny rivers of icy cold. His fingers trembled. The pencil moved over the page. Garth was first puzzled, then perturbed, then lost in a vast unease.
Here and there upon this earth are fields where men, looking backward, see how the stream of history shifted.
There is a field in Greece.
Xerxes gave his orders to his captains. He waited while his host was led forth. Footmen, archers, men with slings. The cavalry would not be of value, for the barbarians, up there, were in a narrow mountain pass. It did not matter. The light-armed troops were more than capable of dispelling these wild tribesmen. By noon, or the middle of the afternoon, the way would be clear to the peninsula beyond. Thus reasoned Xerxes.
When the night came the barbarians were still holding. Tomorrow, Xerxes thought, his troops would be victorious.
Tomorrow came and fresh troops went forth. And eventually the news came back to where Xerxes waited that his army had been routed and was fleeing in disorder.